An Electronically Driven Improper Ferroelectric: Tungsten Bronzes as Microstructural Analogs for the Hexagonal Manganites
An Electronically Driven Improper Ferroelectric: Tungsten Bronzes as Microstructural Analogs for the Hexagonal Manganites
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DOI：
10.1002/adma.201903620
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发表时间：
2019-08-07
影响因子：
29.4
通讯作者：
Morrison, Finlay D.
中科院分区：
文献类型：
--
作者：
McNulty, Jason A.;Tran, T. Thao;Morrison, Finlay D.
由于观察到铁性畴壁（DW）的性质可以显着不同的散装材料中，它们形成，它已经意识到，畴壁工程提供了令人兴奋的新的机会，纳米电子和纳米器件架构。报道了一种新型的六方钨青铜结构的反常铁电体CsNbW_2O_9。粉末中子衍射和对称模分析表明，不适当的转变（T-C = 1100 K）涉及的晶胞三倍，让人想起的六角稀土锰氧化物。然而，与锰氧化物相反，CsNbW 2 O 9中的对称性破缺是电子驱动的（即，纯粹的位移）通过二阶Jahn-Teller效应，与锰氧化物的几何驱动的倾斜机制形成对比。尽管如此，CsNbW 2 O 9显示出与锰氧化物中发现的那些相同种类的畴显微结构，例如特征性的六畴“三叶草”顶点和具有极性不连续性的DW部分。发现一个全新的材料系统，与域模式已经知道在锰氧化物中产生有趣的功能，是重要的新兴领域的DW纳米电子学。
Since the observation that the properties of ferroic domain walls (DWs) can differ significantly from the bulk materials in which they are formed, it has been realized that domain wall engineering offers exciting new opportunities for nanoelectronics and nanodevice architectures. Here, a novel improper ferroelectric, CsNbW2O9, with the hexagonal tungsten bronze structure, is reported. Powder neutron diffraction and symmetry mode analysis indicate that the improper transition (T-C = 1100 K) involves unit cell tripling, reminiscent of the hexagonal rare earth manganites. However, in contrast to the manganites, the symmetry breaking in CsNbW2O9 is electronically driven (i.e., purely displacive) via the second-order Jahn-Teller effect in contrast to the geometrically driven tilt mechanism of the manganites. Nevertheless CsNbW2O9 displays the same kinds of domain microstructure as those found in the manganites, such as the characteristic six-domain "cloverleaf" vertices and DW sections with polar discontinuities. The discovery of a completely new material system, with domain patterns already known to generate interesting functionality in the manganites, is important for the emerging field of DW nanoelectronics.